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Head-to-head · Code Duplication Detection Tools

Fallow vs Simian Similarity Analyzer

  • Updated Oct 2026
  • Both researched from official sources
  • 6 checks side by side
Higher score Fallow #4 in Code Duplication Detection Tools 6.9/10 Free plan · 30-day trial Free planFree trial✓ 3 of 4 features Visit Fallow
Simian Similarity Analyzer #7 in Code Duplication Detection Tools 6.6/10 Open source Free plan✓ 3 of 4 features Visit Simian

Fallow leads on 0 checks, Simian Similarity Analyzer on 1, and 5 are even. Who comes out ahead on the 6 yes/no, price and count checks where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scoreFallow · 6.9/10
  • Free planboth
  • Free trialonly Fallow

Fallow scores higher on our rubric for code duplication detection tools: 6.9 against 6.6 out of 10; our editors rank them #4 and #7.

Simian Similarity Analyzer leads on supported languages: 19 versus 2. On ci/pr reporting, Fallow gives you Pull_request where Simian Similarity Analyzer offers Ci.

Fallow is the better fit for small teams enforcing duplication gates in CI. Simian Similarity Analyzer is the better fit for broad-language duplicate checks in build pipelines.

  • Fallow fits best

    Small teams enforcing duplication gates in CI

  • Simian Similarity Analyzer fits best

    Broad-language duplicate checks in build pipelines

Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.

Side by side

Feature Fallow 6.9/10 Visit ↗ Simian Similarity Analyzer 6.6/10 Visit ↗
At a glance
Editor score 6.9 6.6
Ranking #4 in Code Duplication Detection Tools #7 in Code Duplication Detection Tools
Best for Small teams enforcing duplication gates in CI Broad-language duplicate checks in build pipelines
Pricing model Free plan + paid Free
Starting price $20/seat/mo Open source
Free plan ✓ ✓
Free trial 30 days —
Deployment Cloud, Self-hosted, Browser extension Self-hosted
Platforms Web, Windows, macOS, Linux Windows, macOS, Linux
Support Email, Community, Docs Email, Community, Docs
Integrations 4 integrations 1 integrations
Built for Solo, Small business, Mid-market, Enterprise Solo, Small business, Mid-market, Enterprise
Features Fallow 3/4 · Simian Similarity Analyzer 3/4
Near-duplicate detection ✓ ✓
Duplication gates ✓ ✓
Trend visualisation Not checked yet —
Open-source option ✓ ✓
Specs
Supported languages 2 19 (best)
CI/PR reporting Pull_request Ci
Our review
Pros
  • Free MIT scan runs in the terminal, CI, VS Code, and coding agents
  • Baseline and changed-since analysis can focus CI checks on new duplication
  • Multiple detection modes, near-miss analysis, and CI output formats
  • Supports 19 languages and near-duplicate matching
  • Configurable thresholds plus include and exclude file filters
  • Gradle and build-pipeline integration with duplication failure gates
Cons
  • Analysis is limited to TypeScript and JavaScript projects
  • Near-miss detection is limited to function-scoped clones with small structural edits
  • Production function-call data requires the separate paid Runtime service
  • Command-line workflow may not suit teams seeking a visual interface
  • No trend visualisation is provided
  • Self-hosted deployment requires teams to manage the runtime
Our verdict

Fallow is a codebase analysis tool for TypeScript and JavaScript projects, suited to developers and teams who want duplication checks in their everyday workflow or CI. Its free MIT scan detects duplicated code alongside dead code,…

Read the review →

Simian Similarity Analyzer is an open-source, language-agnostic command-line tool for finding duplicated blocks in source code and other human-readable files. It is aimed at teams that need duplicate checks across large codebases, from…

Read the review →
  1. FallowCode Duplication Detection Tools 6.9Free plan · 30-day trial
  2. Simian Similarity AnalyzerCode Duplication Detection Tools 6.6Open source

Strengths and trade-offs

  • Fallow — where it wins

    • Free MIT scan runs in the terminal, CI, VS Code, and coding agents
    • Baseline and changed-since analysis can focus CI checks on new duplication
    • Multiple detection modes, near-miss analysis, and CI output formats

    Where it doesn't

    • Analysis is limited to TypeScript and JavaScript projects
    • Near-miss detection is limited to function-scoped clones with small structural edits
    • Production function-call data requires the separate paid Runtime service

  • Simian Similarity Analyzer — where it wins

    • Supports 19 languages and near-duplicate matching
    • Configurable thresholds plus include and exclude file filters
    • Gradle and build-pipeline integration with duplication failure gates

    Where it doesn't

    • Command-line workflow may not suit teams seeking a visual interface
    • No trend visualisation is provided
    • Self-hosted deployment requires teams to manage the runtime
  • Fallow6.9/10 · Free plan · 30-day trial

    A free TypeScript and JavaScript duplication scanner with CI gates and optional paid runtime insights.

    Visit FallowFull verdict →
  • Simian Similarity Analyzer6.6/10 · Open source

    A configurable, language-agnostic duplicate checker for build pipelines.

    Visit SimianFull verdict →

More comparisons

All code duplication detection tools comparisons → · Full ranking →

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Last updated · How we research and update